This contour plot shows the progress of the extreme drought at Manilla up to January 2019. Colours show rainfall shortages as percentiles. Dates plot along the top, and durations down the side.
One month rainfall totals (on the top row)
By January 2019, there had been six months without serious monthly rainfall shortages. The months of serious rainfall shortage (light brown) were earlier, in May, June and July 2018. The only other month with such low rainfall was September 2017.
Droughts lasting less than one year (rows 2, 3, 4, 5, 6, 9)
As the effects of low monthly rainfall added up, extreme droughts appeared (dark brown). That is, rainfall totals below the 1st percentile. (They are the lowest rainfall totals, that have occurred in less than 1% of the historical record.)
By June 2018, the 2-month and 3-month totals were already extreme shortages. Similarly, by July, the 3-month, 4-month, and 5-month totals were extreme shortages. By September 2018, extreme shortages extended as far as the 9-month total. That total, adding up the nine months from January to September 2018, included only one month (February) that had rainfall above normal.
In these durations of less than one year, extreme droughts were rare after September 2018. Because the last six months had no serious monthly shortages, the final month (January) includes no serious shortages for durations from 2 months up to 6 months.
Droughts of 1 year to 2 year duration (rows 12, 15, 18, 24)
By August 2018, an extreme 15-month drought appeared. That 15-month total then included not only the dry months of winter 2018, but also the dry month of September 2017. By September 2018, the 15-month total became the driest on record (400 mm). By October all four droughts in this group (12-, 15-, 18-, and 24-month droughts) were extreme. This became true again in January 2019. By that date, some of the dry months of 2017 were no longer included, but dry months in the current summer replaced them in the total.
A similar contour plot with data to October 2018 is here.
A line graph of the rainfall status for January 2019 reveals that extreme shortages also exist now at the much longer durations of six years and seven years that are not included in this contour plot.
The following notes include:
Classes of rainfall shortage
Rainfall rate versus percentile rank
Limitations of this analysis